Engineers have been testing pavement for weeks before Endeavour's trip

Leading up to the space shuttle Endeavour's planned two-day trek Friday and Saturday to the California Science Center, several Southern California engineering firms spent weeks testing the pavement along the 12-mile route and making other preparations.

"We wanted to evaluate whether or not there's the potential for the roads to fail under the load of the shuttle and perhaps the transport would be stuck," said Paul Soltis, geotechnical operations director of Twining Inc. in Long Beach.

Twining was responsible for testing asphalt-paved access roads along the perimeter of Los Angeles International Airport, where the shuttle's journey starts.

To strengthen the roads, workers are installing steel plates to help distribute the shuttle's weight.

On Thursday, Encon Construction was still placing metal plates along part of the shuttle's route, welding some together and surrounding them with asphalt.

The Anaheim engineering firm is renting 2,700 plates for the project. Two hundred were used for LAX roads, with the rest for city streets, Encon President Michael Volchok said.

"It's a big endeavor, pardon the pun," Volchok said. "We brought about 250 truckloads of these plates, and we lay them with forklifts. We've actually depleted the entire supply in Los Angeles and we've brought them in from San Diego, Phoenix and Las Vegas."

Each 8-by-10-foot plate weighs 3,300 pounds. The inch-thick metal pieces are coated with an anti-slip surface to avoid problems with vehicles and pedestrians along the route.

In the city of Inglewood, Encon was placing pedestrian barricades around The Forum as well as "no parking" signs in various areas.

Volchok's company also has been removing obstacles that could obstruct the shuttle's course between the airport and its final destination. That includes center medians and K rails, which are protective concrete barrier used as highway dividers.

"We're demolishing that and after it passes through, we'll rebuild it," Volchok said.

The steel plates also will be removed after the shuttle passes. That process will take about four days.